1. Field of Invention
This invention relates to an impedance standard substrate and a correction method for adjusting a vector network analyzer. More particularly, the present invention is related to an impedance standard substrate with double-sided contacts and a correction method for adjusting the vector network analyzer.
2. Related Art
Generally speaking, conventional vector network analyzers are patented as shown in U.S. Pat. No. 6,348,804 to Evers et. al entitled “Vector Network Analyzer”, U.S. Pat. No. 5,047,725 to Strid et.al entitled “Verification and a correction method for an error model for a measurement network” and U.S. Pat. No 4,858,160 to Strid et. al entitled “System for setting reference reactance for vector corrected measurement”. As mentioned above, the conventional vector network analyzers utilize one or two radio frequency sources (RF source) to provide a signal in high frequency, and two measuring ports for transmitting the signal to a device under test (DUT). Then, a Test Set for testing said signal utilizes Directional Couplers or Directional Bridge to separate the signal transmitting to DUT (incident signal) from the signal reflecting from the signal transmitting to DUT (reflective signal). The frequency of the incident signal and the frequency of the reflective signal shall be lowered by LNB made of LO source and Mixer, and then the processes of filtering the digital signals, amplifying the digital signals, converting the digital signals and displaying the measurements data are performed.
The incident coefficient and the reflective coefficient shall be measured with high precision in measurement of high frequency circuits. And the measurement system adjusts the error of the measurement by the error factor of the incident coefficient and the reflective coefficient.
As mentioned above, the error factor is determined and defined by measuring the known and given standard impedance and comparing said given standard impedance with the measurement data that we get. As we know, there are different standard impedances, however, the standard impedance comprising open-circuits, short-circuits, load-circuits and thru-circuits is usually taken to be a standard reference. As shown above, said measuring port of the vector network analyzer comprises a probe utilized to be in contact with the contacts of the open-circuits, the short-circuits, the load-circuits and the thru-circuits separately so as to define the error factor of the vector network analyzer and adjust the vector network analyzer through the error factor and the given standard impedance.
As shown above, the standard impedance is disposed at one side of a substrate as named an impedance standard substrate. Namely, the conventional impedance standard substrate has one-sided contacts. However, the substrate (one of DUT for measurement) utilized in ball grid array packages (BGAs) has double-sided contacts so that after said one of the probes is adjusted at the upper side of the substrate, said probe shall be rotated at 180 degrees and disposed at the lower side of the substrate to measure the substrate. Specifically, the probes shall be contacted to two contacts of the thru-circuits located at the upper side and the lower side of the substrate when the thru-circuits are under measurement. Accordingly, the rotation of the probes will not be avoided. In addition, the rotation process shall be performed through complex mechanism and affects the precision of the measurement.
Therefore, providing another impedance standard substrate and a correction method for adjusting the vector network analyzer to solve the mentioned-above disadvantages is the most important task in this invention.